1. Field of the Invention
The present invention relates to a carrier unit for a semiconductor device provided with an electrode sheet and semiconductor socket using the same.
2. Description of the Prior Art
A socket used for a burn-in test for a semiconductor device to be mounted to electronic equipment is generally referred to as an IC socket. In a test for KGD (known Good Die) which is a tested acceptable bare chip as a conforming item among the semiconductor devices, the KGD is mounted to a portion of the IC socket for accommodating the bare chip by a carrier unit detachachable therefrom, as disclosed, for example, in Japanese Patent Application Laid-open Nos. 2004-047186 and 2004-220865.
As disclosed also in Japanese Patent Application Laid-open No. 2004-047186, the carrier unit includes, as main elements, a carrier housing having a portion for accommodating a bare chip, an electrode sheet disposed on a inner bottom of the accommodating portion of the carrier housing via an elastic sheets a pressing lid for pressing a group of electrodes in the bare chip to a group of bumps in the electrode sheet, and a latch mechanism for selectively retaining the pressing lid on the carrier housing.
The electrode sheet as a contact sheet (trade mark) has a plurality of bumps formed, for example, of copper opposite to the group of electrode in the bare chip to be electrically connected thereto. A tip end of the respective bump is projected from a surface of the electrode sheet thereof at a predetermined height.
The pressing lid includes a pressing body having a pressing surface to be in contact with a surface opposite to a connecting surface on which the group of electrodes is formed, a lid body for accommodating a base portion of the pressing body, and a plurality of springs arranged in a space between the base of the pressing body and the inner surface of the lid body, for biasing the pressing body to the bare chip as disclosed, for example, in Japanese Patent Application Laid-open No. 2000-3768.
In such a structure, as shown, for example, in FIGS. 27A and 27B, when a pressing lid is arranged on a surface of a bare chip 2 located relative to bumps 4Bi (i=1 to n, n is a positive integer) of an electrode sheet 4 preliminarily disposed on a carrier housing 8 via an elastic sheet 6, the bare chip 2 is initially placed on the electrode sheet 4. The positioning of the electrode section of the bare chip 2 relative to the bumps 4Bi of the electrode sheet 4 is carried out while using, for example, a predetermined image-recognition device. The bumps 4Bi are arranged solely in one row generally at a center of the electrode sheet 4.
Then, when the pressing lid is mounted to the interior of the carrier housing 8, the lid body is mounted on an accommodation portion of the carrier housing 8 so that the outer circumference of the lid body is guided by a guide member provided on the carrier housing 8. Thereafter, tip ends of hook members of the latch mechanism are rotated to be closer to each other and engaged with the upper surfaces of projections of the lid body. As a result, the pressing lid is retained by the carrier housing 8.
At that time, in a case of a so-called center pad type bare chip wherein the plurality of bumps 4Bi are arranged in one row solely generally at a center of the electrode sheet 4 as shown in FIGS. 27A and 27B, the bare chip 2 may incline after it is placed on the bumps 4Bi of the electrode sheet 4, whereby a gap CL may be formed on one side between the electrode surface of the bare chip 2 and the surface of the electrode sheet 4.
Then actually, a predetermined gap is formed between the outer circumference of the carrier housing 8 and the fitting portion of the guide member. In addition thereto, due to the individual variance in biasing force of the above-mentioned respective springs, a pressing surface 10a of a pressing body 10 inclines in one direction as shown in FIG. 27C. That is, the tip ends of the bumps 4Bi are pressed by a deflected pressure caused by the bare chip 2.
Accordingly, there is a risk in that the distribution of the pressures and/or contact areas at tip ends of the plurality of bumps 4Bi may scatter larger while exceeding a tolerance whereby the electric connection of the tip ends of the bump on a part of the bumps 4Bi with the electrodes of the bare chip 2 becomes unreliable.
As shown in Japanese Patent Application Laid-open No. 2004-047186, as a countermeasure to such a trouble, a electrode sheet is proposed, capable of providing dummy bumps adjacent to the vicinity of the bumps on the electrode sheet. Since the tip ends of the dummy bumps are brought into contact with part of the bare chip 2, a moving amount of the bump 4Bi of the bare chip 2 in the height direction is restricted and the posture of the bare chip 2 is stabilized to be approximately parallel to the surface of the electrode sheet without any inclination.